I make about 45k p/h by cleaning herbs, I also made about 5M after getting to about 80, the herbs fluctuate though so I ended up losing like 2M of the profit the next day.
Clearning herbs is the way to go. http://www.sixfeetunder.ws/calcs/herblore.php
Use that site too see what herbs you lose profit and what herbs you gain.
Best to bot it of course legit would take forever.